Is this 55" Hitachi a good buy? (lines on screen)

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Just out of curiosity I put my blue ring tester on the transformers and there is one that does not ring at all. I tried all combinations of pins.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

No, they very rarely fail.

Things to look out for would be ICs near the MOSFETs/IGBTs.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Do transformers go pop when they fail? I have been over the board with a jewelers loop and cant find anything that looks broken.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

No IPMs, all discrete. Good on Hitachi...

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

It would be a rather large chip under a heat sink, right? I don't see one...

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

On LG, the rightmost board is Z, but everyone else uses X.

I doubt this set uses IPMs. It will all be discrete if it is a Hitachi. That is, all MOSFETs, IGBTs and diodes. But if you post a picture, I'll be able to tell for sure.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I have read that IPMs often produce a pop when thy fail. How can I identify which chip is an IPM?

Also, aren't the two boards on the sides of the plasma panel normally called y and z? I just noticed this hitachi calls the one to the right x.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I will have to bring home my good meter from work tomorrow and test.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Possibly, do you have Va/Vda/Vdata?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

With the power unhooked from Xsus and Ysus (all the ribbons are still connected, is this ok?) there is no Vs coming off of the PSU. So I guess the pop came from the PSU? But the TV still powers on with sound... Possible just the Vs rail broke?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

with X-sustain disconnected?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Yeah, trace the wires from Xsus to PSU.

The harness that goes from psu to xsus does not include Vs in any of the labels. Only the harness that connects X and Y have the Vs label. In the service manual it shows where a test pin for Vs on the PSU. I tested it, and I get nothing...

EDIT: The harness that is going from PSU to Xsus is labeled "VSI" "VAI" and "VCC"... Is VSI the same as VS?

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Yeah, trace the wires from Xsus to PSU.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Vs is only labeled on xsus and ysus. Shouldn't vs be coming directly from the psu somewhere?

Hold on, I see the test point on the psu. Let me check...

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I dunno then, any Vs with Xsus and Ysus disconnected?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

But the TV runs with sound, but no VS.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I remember one Pioneer/NEC I had shut down with no Ysus making identification of shorts difficult. In fact once I plugged it in it flashed red/green continuously until I reset it.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

in this TV Ysus and Xsus are connected directly through a harness. PSU goes to Xsus which goes to Ysus. I'm afraid its bad because with the Ysus unhooked, Vs was non existent on Xsus.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I would find it hard to believe the X-sus to be bad. It's completely separate from the Y-sus -- it's not even connected to it through the panel. There's no direct connection between the scan and sustain electrodes, just a gap where plasma forms.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

With the power to ysus unhooked vs falls to -0.4mv when I turn the tv on. Power board daisy chains to xsus then from there to ysus. I was sitting directly in front of the xsus when I heard the pop. It didn't sound like xsus but I could be wrong.

I don't 100% trust this meter, I just found it in a drawer. I will bring my nice one home again and test again. If this xsus board is bad too I'm going to cry.